Medium density polyethylene or MDPE is a best alternative to HDPE and LDPE. As the material has balanced shrinkage properties compared to that of HDPE and LDPE, some cable manufacturers prefer to use MDPE as outer sheath. Properties such as specific gravity, tensile strength and elongation of MDPE are in between HDPE and LDPE. MDPE shows better abrasion resistance than LDPE. MDPE is easily available and hence not highly priced, that makes it attractive to cable makers.
MDPE is supplied in natural or black color in 25 kg bags. The bags are sealed in order to avoid entry of moisture. Once the bag is opened, the material shall be used immediately. If decide to use later after opening the bag, it is advisable to dry the material in a dryer to remove any possible moisture.
Let us see how to specify the requirements when we need to order MDPE to a supplier. Here we discuss the specification requirements of Medium Density Polyethylene (MDPE) that is intended for sheathing optical fiber cables.
– The material shall contain uniformly dispersed carbon black of such a quantity that good weather resistance is reached.
– The carbon black shall be of Channel or Furnace type.
– The particle size (diameter) of carbon black shall be less than 20 nm on an average.
– The material shall not generate hydrogen in sufficient quantities to degrade the performance
of optical fiber cable transmission.
|S #||Attribute||Value||Test Method|
|1||Melt Flow index, 190°C, 2.16 kg||≤ 10 g/10 min||ASTM 1238|
|2||Oxidation Induction Time, 180°C||≥ 30 minutes||ASTM D 3895|
|3||Carbon Black Content||25 ± 0.25 %||ASTM D 1603|
|4||Carbon Black Dispersion||Uniform||ASTM D 3349|
|5||Tensile Strength||≥ 18 MPa||ASTM D 638|
|6||Elongation at Break||> 400 %||ASTM D 638|
|7||Shore D Hardness||≥ 55||ISO R 868|
Test Certificate: Each incoming delivery/ batch shall be accompanied by a test certificate.
Packing: The material shall be packaged in standard commercial containers or bags, so constructed as to ensure safe transportation.